Tuesday, 4 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
On 24 May 2011, Western and Central Oklahoma experienced an outbreak of tornadoes, including one rated EF-5 and two rated EF-4. The extensive observation network in this area, including the WSR-88D radars, Collaborative Adaptive Sensing of the Atmosphere (CASA) radars, Oklahoma Mesonet, and National Weather Service (NWS) and Federal Aviation Administration METAR, makes this an ideal case to explore forecast capabilities applicable to the Warn-on-Forecast (WoF) concept. The CAPS real-time forecasting system had good success in simulating these storms, using these data but improvements might be expected using more sophisticated microphysics or an ensemble of models with microphysics diversity. The aim of this study is to examine the impact of using four different microphysics parameterization schemes, including the Lin 3-ice microphysics scheme, Weather Research and Forecasting (WRF) single-moment 6-class (WSM6) microphysics scheme, Milbrandt and Yau (MY) single moment bulk microphysics scheme, and MY double moment bulk microphysics scheme, on the genesis and evolution of simulated tornado-like vortices (TLVs) as compared to each other and reality. Three tornadic supercells from this event are individually investigated using the Advanced Regional Prediction System (ARPS) model developed at the Center for Analysis and Prediction of Storms (CAPS). Analyses are produced about 35 minutes prior to the estimated tornadogenesis time for each of the three supercells using the ARPS three-dimensional variational data assimilation (3DVAR) system and ARPS data assimilation system (ADAS) complex cloud analysis using the 12-km North American Mesoscale (NAM) model for the background fields and lateral boundary conditions. Next, a 5-minute ARPS incremental analysis update (IAU) is executed with increments added every 30 seconds. Finally, the ARPS model is performed out to 90 minutes to capture TLV genesis and evolution. The modeled TLV tracks, estimated from vorticity and wind fields, are verified against the estimated tornado locations determined from the NWS damage surveys.
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